1. Field of the Invention
The present invention relates to an apparatus and a method for removing impurities from aqueous hydrogen peroxide to produce ultra-pure aqueous hydrogen peroxide which is used, in particular, in the electronics industry.
2. Description of the Related Art
Aqueous hydrogen peroxide is used in the electronics industry, for example, for cleaning silicon wafers and the like.
Aqueous hydrogen peroxide which is produced industrially is contaminated by various impurities such as substances originating from metals, for example, iron, aluminum, sodium, calcium, lithium, zinc, lead, chromium, nickel, magnesium, etc., or organic materials originating from various additives, phosphorus, and the like during production, storage, transportation, and so on.
However, since the contamination of aqueous hydrogen peroxide with such metal-originated substances or organic materials has much influence when used in the electronics industry, on the deterioration of the quality of the products, i.e., the silicon wafers, it is essential to remove such impurities.
In recent years, with the advance in precision of electronics such as increase of an integration degree of an IC, the requirement for the removal of impurities has become more stringent. Many proposals have been made on the removal of the impurities such as the metal-originated substances or the organic materials, but none of them reaches a satisfactory level.